diff --git a/docs/design/biking.md b/docs/design/biking.md
index a46722f83c..c2bb671dda 100644
--- a/docs/design/biking.md
+++ b/docs/design/biking.md
@@ -3,3 +3,31 @@
 ## Bike lanes
 
 How do we model bikes merging to a driving lane to make a left?
+
+## General modeling
+
+Bikes are just like cars and can use all the same code, right? Except...
+
+- different speeds
+- can use bike or driving lanes
+- they dont park or unpark
+	- actually, how does a ped start/stop using a bike?
+	- modeling bike lockup locations is overkill. in practice not a
+	  problem. fixed 60s penalty to start/stop biking. penalty happens on
+	  the sidewalk, then they spawn onto the bike/driving lane at the very end
+- they can _maybe_ overtake on a bike lane?
+	- nah, that should be modeled as two bike lanes (or a bike and driving lane) and normal lanechanging behavior
+- different rendering
+- dont want to use CarID; could maybe rename it VehicleID, but then bike-specific code (like rendering) gets weird
+
+Because of the orchestration with walking/biking models, I'm tempted to try to share some common code, but keep things a bit separate. However, if they're separate...
+
+- driving lookahead needs to see bikes and vice versa
+	- do the SimQueues need to be state that both models can access?
+
+
+Do this in a branch for sure. Roughly:
+- introduce BikeID, the rendering, stubs for spawning
+- lift SimQueues into Sim
+- refactor lookahead
+- add biking model
diff --git a/docs/design/sim.md b/docs/design/sim.md
index 87a7acbec3..02fba12bda 100644
--- a/docs/design/sim.md
+++ b/docs/design/sim.md
@@ -17,6 +17,8 @@ currently begin departing, it'll keep trying every tick.
 
 - serde tricks
 - unit tests
+- https://gafferongames.com/post/deterministic_lockstep/
+- https://gafferongames.com/post/floating_point_determinism/
 
 ## Modeling choices
 
diff --git a/docs/project/references.md b/docs/project/references.md
index f9e5e4727b..e46705f759 100644
--- a/docs/project/references.md
+++ b/docs/project/references.md
@@ -10,6 +10,9 @@
 
 - Seattle Times Traffic Lab
 - https://www.citylab.com/transportation/2018/08/is-it-time-to-rethink-what-a-bike-lane-is/568483/
+- http://openseattle.org/
+- https://igniteseattle.com/
+- http://seattlegreenways.org/
 
 ## Similar projects
 
diff --git a/sim/src/fsm.rs b/sim/src/fsm.rs
new file mode 100644
index 0000000000..eea76945e7
--- /dev/null
+++ b/sim/src/fsm.rs
@@ -0,0 +1,80 @@
+use dimensioned::si;
+use geom::Pt2D;
+use map_model::{BuildingID, BusStopID, LaneID, Map, TurnID};
+use {CarID, Distance, ParkingSpot, RouteID, Time};
+
+// This is experimental for now, but it might subsume the entire design of the sim crate.
+
+// TODO From a conversation with Julian: have to prune the search dramatically. After hopping in a
+// car, we do have the option of parking anywhere, but we really only want to try to park close to
+// the goal, which we can't plan in advance anyway.
+//
+// Possibly want a high- and low-level plan. The high-level one roughly plans TripLegs.
+
+// TODO It's very tempting to have a different action for each modality. CrossDrivingLane,
+// CrossSidewalk.
+enum Action {
+    // Cars (including buses) and pedestrians
+    CrossLane(LaneID),
+    CrossTurn(TurnID),
+
+    // Only cars
+    ParkingCar(CarID, ParkingSpot),
+    UnparkingCar(CarID, ParkingSpot),
+    // TODO Lanechanging
+
+    // Only pedestrians
+    CrossLaneContraflow(LaneID),
+    CrossPathFromBuildingToSidewalk(BuildingID),
+    CrossPathFromSidewalkToBuilding(BuildingID),
+    WaitForBus(BusStopID, RouteID),
+    // (from, to)
+    RideBus(BusStopID, BusStopID),
+
+    // Only buses
+    DeboardPassengers(BusStopID),
+    BoardPassengers(BusStopID),
+}
+
+impl Action {
+    // These are always lower bounds, aka, the best case.
+    fn cost(&self, map: &Map) -> Time {
+        // TODO driving speed limits and these could depend on preferences of the individual
+        // ped/vehicle
+        let ped_speed = 3.9 * si::MPS;
+
+        match *self {
+            // TODO wait, we need to know if a ped or car is crossing something
+            Action::CrossLane(id) => map.get_l(id).length() / map.get_parent(id).get_speed_limit(),
+            Action::CrossTurn(id) => {
+                map.get_t(id).length() / map.get_parent(id.dst).get_speed_limit()
+            }
+            Action::ParkingCar(_, _) => 20.0 * si::S,
+            Action::UnparkingCar(_, _) => 10.0 * si::S,
+            Action::CrossLaneContraflow(id) => map.get_l(id).length() / ped_speed,
+            Action::CrossPathFromBuildingToSidewalk(id)
+            | Action::CrossPathFromSidewalkToBuilding(id) => {
+                map.get_b(id).front_path.line.length() / ped_speed
+            }
+            // TODO Could try lots of things here...
+            Action::WaitForBus(_, _) => 60.0 * si::S,
+            // TODO Cache the expected time to travel between stops
+            Action::RideBus(_stop1, _stop2) => 300.0 * si::S,
+
+            _ => panic!("TODO"),
+        }
+    }
+
+    // After completing this action, how far will we be from the goal?
+    // Does this need to be admissible?
+    // TODO hard to convert distance and time
+    fn heuristic(&self, goal: Pt2D) -> Distance {
+        // TODO
+        0.0 * si::M
+    }
+
+    fn next_steps(&self) -> Vec<Action> {
+        // TODO
+        Vec::new()
+    }
+}
diff --git a/sim/src/lib.rs b/sim/src/lib.rs
index 2ff3661ef8..30a1976f97 100644
--- a/sim/src/lib.rs
+++ b/sim/src/lib.rs
@@ -32,6 +32,7 @@ mod macros;
 
 mod driving;
 mod events;
+//mod fsm;
 mod helpers;
 mod instrument;
 mod intersections;